The present invention refers to an embossing assembly for sheet material, in particular paper, such as tissue paper, toilet paper and the like.
Embossing machines provided with embossing rollers or cylinders supported rotatably at their ends, by means of bearings, in the side panels of the embossing machine frame are known on the market. Such embossing rollers are provided with a sleeve, generally of steel, engraved with the embossing patterns, so as to be able to perform embossing of respective plies of paper which are subsequently coupled together by nested or tip-to-tip coupling, so as to obtain a multi-ply embossed web.
Embossing rollers must be accessible and/or removable both for maintenance (for example, replacement of bearings) and due to the need to change the embossing patterns on the web and thus the engraving on the sleeve of the embossing roller. Removal of the embossing rollers leads to considerable machine stoppages, because it is necessary to remove and re-assemble some parts of the embossing machine due to the difficult accessibility to these embossing rollers. Furthermore, the embossing rollers must be set to make the engravings of the two plies coincide. For this purpose it is necessary to perform a relative transverse and angular adjustment of the rollers. This operation proves to be complex, slow and laborious. For these reasons, machine stoppages for replacement of the embossing rollers are of the order eight hours.
Furthermore, depending upon the diameter and engravings of each embossing roller, it is necessary to vary the center distance between the two embossing rollers. In embossing machines of the prior art, the center distance between the embossing rollers is generally fixed since the embossing roller supports are integral with the side panels of the frame in a fixed position, or the housing of the bearing is even formed in the side panels themselves.
There are other embossing machines in which an embossing roller is mounted on a movable side panel which is pivoted to a fixed side panel. In these machines adjustment of the center distance between the embossing rollers is achieved by adjusting the rotation and thus the proximity of the movable side panel to the fixed side panel. This solution makes production of the machine costly and adjustment of the center distance complex.
European patent application EP 0 928 682 discloses an embossing machine in which an embossing roller is supported rotatably at its ends by two movable portions of the side panel, pivoted to the two fixed side panels of the machine frame. In this manner, to carry out replacement of the embossing rollers, the two movable portions of the side panel are rotated so as to move the two embossing rollers apart and leave space for removal thereof.
Even if this system speeds up embossing roller changes compared to embossing machines in which the rollers are mounted in fixed side panels, there still remain therein some drawbacks in that the access space is in any case limited, it is not possible to carry out simultaneous replacement of both rollers, and adjustment of the distance between the rollers is complex.